Solid secondary battery and method of manufacturing the same

Abstract

A solid secondary battery and a method of manufacturing the same are provided. The solid secondary battery includes a cathode layer, an anode layer, a solid electrolyte layer provided between the cathode layer and the anode layer, wherein the cathode layer includes a cathode current collector and a cathode active material layer provided on one surface or two surfaces of the cathode current collector. The cathode active material layer includes a composite cathode active material, and the composite cathode active material includes a composite of M 2 S, an alkali metal salt, and an inorganic electronic-conductive structure, wherein M is an alkali metal, and the alkali metal is Li or Na. The inorganic electronic-conductive structure has an electronic conductivity of 11×10 −3 S/cm or more, and the composite includes a solid solution of the M 2 S and the alkali metal salt.

What is claimed is: 
     
         1 . A solid secondary battery comprising:
 a cathode layer;   an anode layer; and   a solid electrolyte layer between the cathode layer and the anode layer,   wherein   the cathode layer comprises a cathode current collector and a cathode active material layer on at least one surface of the cathode current collector,   the cathode active material layer comprises a composite cathode active material, and   the composite cathode active material comprises a composite of M 2 S, an alkali metal salt, and an inorganic electronic-conductive structure, and   wherein   M is an alkali metal,   the alkali metal is Li or Na, and   the inorganic electronic-conductive structure has an electronic conductivity of 1×10 −3  siemens per centimeter (S/cm) or more.   
     
     
         2 . The solid secondary battery as claimed in  claim 1 , wherein
 a size of an M 2 S crystallite obtained from an X-ray diffraction (XRD) spectrum of the composite is less than 10 nanometer (nm), and   the composite comprises a solid solution of the M 2 S and the alkali metal salt.   
     
     
         3 . The solid secondary battery as claimed in  claim 1 , wherein an amount of the inorganic electronic-conductive structure is in a range of about 1 part by weight to about 30 parts by weight with respect to about 100 parts by weight of the composite. 
     
     
         4 . The solid secondary battery as claimed in  claim 1 , wherein
 the inorganic electronic-conductive structure has a form of a zero-dimensional structure, a one-dimensional structure, or a two-dimensional structure and has a length of about 1 micrometer (μm) to about 50 μm and a thickness of about 0.01 μm to about 10 μm, and   the M 2 S has a size of about 0.1 nm to about 10 μm.   
     
     
         5 . The solid secondary battery as claimed in  claim 1 ,
 wherein the inorganic electronic-conductive structure comprises:
 a transition metal sulfide; 
 a sulfide of at least one metal of metals of Groups 3 to 5 of the periodic table, or a combination thereof; 
 at least one metal selected from among titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, niobium, tantalum, molybdenum, and tungsten; or 
 a combination thereof, and 
   wherein the inorganic electronic-conductive structure further comprises:
 at least one metal oxide selected from among VO 2 , ReO 2 , CrO 2 , SnO 2 , TiO 2 , ZrO 2 , Al 2 O 3 , TeN, TiN, TiO, TiOx (wherein 0.75<x<1.45), Ti n O 2n-1  (wherein 4<n<10), ReO 3 , CrO 3 , and VO 3 ; and 
   at least one metal material selected from among ZrS 2 , FeS, FeS 2 , CuS, Cu 2 S, CuS 2 , Cu 9 S 8 , Cu 7 S 4 , CoS, CoS 2 , CO 3 S 4 , Co 9 S 8 , NiS, NiS 2 , Ni 9 S 8 , Ni 3 S 2 , VS, VS 2 , V 2 S 3 , V 2 S 5 , VS 4 , NbS 2 , NbS 3 , NbS 4 , NbS 5 , Nb 2 S 3 , Nb 2 S 5 , TaS 2 , TaS 3 , TaS 4 , TaS 5 , Ta 2 S 3 , Ta 2 S 5 , Cr 2 S 3 , CrS 3 , MoS 2 , MoS 3 , MoS 4 , WS 2 , WS 3 , WS 4 , WS 5 , MnS, Mn 2 S 3 , TiS 2 , NiNb 3 S 6 , Cu 2 MoS 4 , and Cu 4 Mo 6 S 8 , or a combination thereof.   
     
     
         6 . The solid secondary battery as claimed in  claim 1 , wherein,
 in an X-ray diffraction (XRD) spectrum of the composite cathode active material, a first diffraction angle of each of a first peak appearing at a diffraction angle (2θ) of about 14.5°±0.5°, a second peak appearing at a diffraction angle (2θ) of about 32.5°±0.5°, and a third peak appearing at a diffraction angle (2θ) of about 58.5°±0.5° in the composite is less than a second diffraction angle of each of a fourth peak appearing at a diffraction angle (2θ) of about 14.5°±0.5°, a fifth peak appearing at a diffraction angle (2θ) of about 32.5°±0.5°, and a sixth peak appearing at a diffraction angle (2θ) of about 58.5°±0.5° in an XRD spectrum of MoS 2  used to prepare the composite, respectively, and   an intensity of the first peak appearing at a diffraction angle (2θ) of about 14.5°±0.5° is less than an intensity of the fourth peak appearing at a diffraction angle (2θ) of about 14.5°±0.5° in the XRD spectrum of the MoS 2  used to prepare the composite.   
     
     
         7 . The solid secondary battery as claimed in  claim 1 , wherein,
 in an X-ray diffraction (XRD) spectrum of the composite,   a first lattice constant (d 1 ) derived from a seventh peak appearing at a diffraction angle (2θ) of 27°±2.0° corresponding to a (111) crystal plane of the M 2 S is larger than a second lattice constant (d 2 ) derived from an eighth peak appearing at a diffraction angle (2θ) of about 27°±2.0° corresponding to a (111) crystal plane of the M 2 S in an XRD spectrum of the M 2 S used to prepare the composite, and   wherein a size of the first lattice constant (d 1 ) is 5.78 angstrom (Å) or more.   
     
     
         8 . The solid secondary battery as claimed in  claim 1 , wherein
 a particle size of the M 2 S is less than or equal to a particle size of the alkali metal salt,   a particle size of the inorganic electronic-conductive structure is greater than a particle size of each of a lithium sulfide and the alkali metal salt, and   the particle sizes of the inorganic electronic-conductive structure, the alkali metal salt, and the M 2 S gradually decrease in order of the inorganic electronic-conductive structure, the alkali metal salt, and the M 2 S.   
     
     
         9 . The solid secondary battery as claimed in  claim 1 ,
 wherein   the cathode active material layer further comprises a solid electrolyte, and   wherein   the solid electrolyte comprises a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, and   an amount of the solid electrolyte is in a range of about 10 parts by weight to about 60 parts by weight, with respect to 100 parts by weight of the cathode active material layer.   
     
     
         10 . The solid secondary battery as claimed in  claim 1 ,
 wherein   the alkali metal salt is a lithium salt or a sodium salt and is a binary compound or a ternary compound, and   wherein   the binary compound comprises: LiI, LiBr, LiCl, LiF, LiH, Li 2 O, Li 2 Se, Li 2 Te, Li 3 N, Li 3 P, Li 3 As, Li 3 Sb, Li 3 Al 2 , LiB 3 , or a combination thereof; or NaI, NaBr, NaCl, NaF, Na 2 O, Na 2 Se, Na 3 N, Na 3 P, Na 3 As, Na 3 Sb, Na 3 Al 2 , NaB 3 , or a combination thereof, the ternary compound comprises Li 3 OCl, LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlC 14 , LiNO 3 , Li 2 CO 3 , LiBH 4 , Li 2 SO 4 , Li 3 BO 3 , Li 3 PO 4 , Li 4 NCl, Li 5 NCl 2 , Li 3 BN 2 , or a combination thereof or comprises Na 3 OCl, NaBF 4 , NaPF 6 , NaAsF 6 , NaClO 4 , NaNO 3 , NaAlO 2 , NaAlCl 4 , NaNO 3 , Na 2 CO 3 , NaBH 4 , Na 2 SO 4 , NasBO 3 , Na 3 PO 4 , Na 4 NCl, Na 5 NCl 2 , Na 3 BN 2 , or a combination thereof, and   a molar ratio of the M 2 S to the alkali metal salt in the composite is in a range of about 50:50 to about 95:5.   
     
     
         11 . The solid secondary battery as claimed in  claim 1 ,
 wherein a particle size of the composite is 2 μm or less.   
     
     
         12 . The solid secondary battery as claimed in  claim 1 , wherein the composite has a two-dimensional form and comprises a carbon-based material. 
     
     
         13 . The solid secondary battery as claimed in  claim 1 , wherein the anode layer comprises an anode current collector and a first anode active material layer on the anode current collector. 
     
     
         14 . The solid secondary battery as claimed in  claim 13 , wherein
 an anode active material of the first anode active material layer comprises at least one selected from a carbon-based anode active material and a metal-based anode active material,   the carbon-based anode active material comprises amorphous carbon, crystalline carbon, porous carbon, or a combination thereof,   the metal-based anode active material comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof, and   the anode active material of the first anode active material layer comprises a mixture of a metal-based anode active material and a carbon-based material, a metal-based anode active material supported on a carbon-based material, or a combination thereof.   
     
     
         15 . The solid secondary battery as claimed in  claim 1 , wherein
 the anode layer comprises an anode current collector and a lithium host layer on one surface of the anode current collector,   the lithium host layer comprises a lithium host structure,   the lithium host structure comprises one or more lithium hosts, wherein the lithium host comprises a carbon-based lithium host, a metal-based lithium host, a polymer-based lithium host, or a combination thereof, and   the solid secondary battery comprises a first inactive member on one side surface of the anode layer.   
     
     
         16 . The solid secondary battery as claimed in  claim 13 , further comprising a second anode active material layer between the anode current collector and the first anode active material layer,
 wherein   the second anode active material layer is a metal layer comprising lithium or a lithium alloy and is a plated layer, and   the first anode active material layer is thicker than the second anode active material layer.   
     
     
         17 . The solid secondary battery as claimed in  claim 1 , wherein
 the solid secondary battery comprises an inactive elastic member on one surface of the cathode layer or the anode layer, or   does not comprise the inactive elastic member.   
     
     
         18 . The solid secondary battery as claimed in  claim 1 ,
 wherein   the solid electrolyte layer comprises a solid electrolyte, a gel electrolyte, or a combination thereof,   wherein   the solid electrolyte comprises a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof,   the gel electrolyte comprises a polymer gel electrolyte,   the sulfide-based solid electrolyte comprises at least one selected from among:   Li 2 S—P 2 S 5 ;   Li 2 S—P 2 S 5 —LiX, X being a halogen element;   Li 2 S—P 2 S 5 —Li 2 O;   Li 2 S—P 2 S 5 —Li 2 O—LiI;   Li 2 S—SiS 2 ;   Li 2 S—SiS 2 —LiI;   Li 2 S—SiS 2 —LiBr;   Li 2 S—SiS 2 —LiCl;   Li 2 S—SiS 2 —B 2 S 3 —LiI;   Li 2 S—SiS 2 —P 2 S 5 —LiI;   Li 2 S—B 2 S 3 ;   Li 2 S—P 2 S 5 —Z m S n , m and n being each a positive number, and Z being one selected from among Ge, Zn, and Ga;   Li 2 S—GeS 2 ;   Li 2 S—SiS 2 —Li 3 PO 4 ;   Li 2 S—SiS 2 —Li p MO q , p and q being each a positive number, and M being one selected from among P, Si, Ge, B, Al, Ga, and In;   Li 7-x PS 6-x Cl x , 0<x<2; Li 7-x PS 6-x Br x , 0<x<2; and   Li 7-x PS 6-x I x , 0≤x≤2, and   comprises an argyrodite-type solid electrolyte, and   wherein the argyrodite-type solid electrolyte comprises at least one selected from among Li 6 PS 5 Cl, Li 6 PS 5 Br, and Li 6 PS 5 I and has a density of about 1.5 gram per cubic centimeter (g/cc) to about 2.0 g/cc.   
     
     
         19 . The solid secondary battery as claimed in  claim 1 , wherein the anode layer comprises
 an anode current collector, and   at least one of the cathode current collector or the anode current collector comprises a base film and a metal layer on at least one surface of the base film, and   wherein   the base film comprises a polymer, the polymer comprising polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof, and   the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.   
     
     
         20 . A method of manufacturing a solid secondary battery, the method comprising:
 performing a first milling of M 2 S and an alkali metal salt;   adding an inorganic electronic-conductive structure to a first-milled product and performing a second milling to obtain a composite;   preparing a cathode by utilizing a composition obtained by adding a binder to the composite and mixing the binder with the composite;   preparing an anode; and   arranging a solid electrolyte layer between the cathode and the anode.